Cidaroida

Cidaroida Temporal range:
Cidaris cidaris
Scientific classification
Kingdom:	Animalia
Phylum:	Echinodermata
Class:	Echinoidea
Subclass:	Perischoechinoidea
Order:	Cidaroida Claus, 1880
Families
Cidaridae Psychocidaridae

Cidaroida is an order of primitive sea urchins, the only living order of the subclass Perischoechinoidea. All other orders of this subclass, which were even more primitive than the living forms, became extinct during the Mesozoic.

Description

Their primary spines are much more widely separated than in other sea urchins, and they have no gills. Other primitive features include relatively simple plates in the test, and the ambulacral plates continuing as a series across the membrane that surrounds the mouth.

List of families

Many different fossil Cidaroid radiola (MNHN).

According to World Register of Marine Species:

• family Anisocidaridae Vadet, 1999 †
• super-family Cidaridea Gray, 1825
  • family Cidaridae Gray, 1825
  • family Ctenocidaridae Mortensen, 1928a
  • family Paurocidaridae Vadet, 1999a †
• family Diplocidaridae Gregory, 1900 †
• family Heterocidaridae Mortensen, 1934 †
• super-family Histocidaroidea Lambert, 1900
  • family Histocidaridae Lambert, 1900
  • family Psychocidaridae Ikeda, 1936
• family Miocidaridae Durham & Melville, 1957 †
• family Polycidaridae Vadet, 1988 †
• family Rhabdocidaridae Lambert, 1900 †
• family Serpianotiaridae Hagdorn, 1995 †
• family Triadocidaridae Smith, 1994c †

• 
  Eucidaris tribuloides.
• 
  Phyllacanthus imperialis.
• 
  Prionocidaris hawaiiensis.
• 
  Stylocidaris affinis
• 
  Balanocidaris marginata (fossil species).

See also

• World Register of Marine Species link: Cidaroida Claus, 1880 (+species list)
• Barnes, Robert D. (1982). Invertebrate Zoology. Philadelphia, PA: Holt-Saunders International. p. 980. ISBN 0-03-056747-5.
• National History Museum. "Cidaroida". Retrieved 20 Dec 2009.